Abstract 732: A practical strategy to pancreatic cancer immunotherapy using resected human tumor lysate vaccines remodeled to express α-gal epitopes

Abstract

Abstract Cancer immunotherapy is a potential treatment for pancreatic ductal adenocarcinoma (PDAC) patients. As the predominant natural Ab found in humans, anti-Gal accounts for approximately 1% of immunoglobulins. The ligand of anti-Gal, “α-gal epitope (Galα1-3Galβ1-4GlcNAc-R),” is a major carbohydrate antigen, expressed by non-primate mammals, New World monkeys. One useful application of anti-Gal abundance is the enhancement of the immunogenicity of tumor-associated antigens (TAAs) that promote effective uptake by antigen-presenting cells (APCs). To develop an effective vaccine-based immunotherapy for PDAC, we hypothesized that resected tumor tissue lysates from patients might be an attractive source of PDAC-associated TAAs vaccination. This study presents a novel immunotherapy expressing α-gal epitopes using freshly obtained human PDAC tumor tissue homogenates from patients. Tumor and normal pancreatic tissue specimens were obtained from 10 patients at the time of surgical exploration for primary PDAC. To synthesize α-gal epitopes on either tumor membranes or normal pancreatic tissue membranes, we employed recombinant α1,3 galactosyltransferase (α1,3GT). PDAC membranes or normal pancreatic tissues were homogenized, and were incubated with UDP-Gal and α1,3GT. α1,3GT KO mice were immunized with pig tissues to produce anti-Gal Ab. The high anti-Gal KO mice were vaccinated by i.p. injection with unprocessed or processed PDAC tumor lysate (α-gal(-) PDAC-ly or α-gal(+) PDAC-ly). The high anti-Gal KO mice were also vaccinated with unprocessed normal or processed normal pancreatic tissue lysate (α-gal(-) N-ly or α-gal(+) N-ly). Effective synthesis of α-gal epitopes was demonstrated after processing of PDAC tumor lysates in Western blot analysis. α-gal(+) PDAC-ly vaccines elicited significant antibody production against multiple TAAs, assessed by ELISPOT (anti-MUC1; α-gal(-) PDAC-ly vs. α-gal(+) PDAC-ly=28.7 vs. 151.8 spots [P=0.0008], anti-mesothelin; α-gal(-) PDAC-ly vs. α-gal(+) PDAC-ly=36.5 vs. 97.2 spots [P=0.029]) and activated multiple tumor-specific T cells, assessed by ELISPOT (MUC1; α-gal(-) PDAC-ly vs. α-gal(+) PDAC-ly=146.0 vs. 828.0 spots [P=0.0009], mesothelin; α-gal(-) PDAC-ly vs. α-gal(+) PDAC-ly= 250.7 vs. 988.0 spots [P=0.021], α-gal(-) N-ly and α-gal(+) N-ly groups did not display significant spots.). To demonstrate in vivo effectiveness, splenocytes from vaccinated KO mice were prepared, and these isolated cells were transferred by i.p. injection into NOD/SCID mice. Then, live PANC1 cells were challenged with s.c. injection. The survival time of NOD/SCID mice received from α-gal(+) PDAC-ly groups was significantly extended (95.0 days) compared with α-gal(-) PDAC-ly groups (45 days, p<0.01). We conclude that α-gal(+) PDAC-ly vaccination may be a practical and effective new immunotherapeutic approach for treating PDAC. Citation Format: Masahiro Tanemura, Kenta Furukawa, Eiji Miyoshi, Hidetoshi Eguchi, Hiroaki Nagano, Katsuyoshi Matsunami, Satoshi Nagaoka, Manabu Mikamori, Kentaro Kishi, Hiroki Akamatsu, Masaki Mori, Yuichiro Doki. A practical strategy to pancreatic cancer immunotherapy using resected human tumor lysate vaccines remodeled to express α-gal epitopes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 732.